Metals

Athe elements have been divided into two classes: metals and non-metals. 80% of the total elements (known till now) are metals. Metals are the good conductor of heat and electricity, they are malleable and ductile. Most of the metals are found in combined state.

Metals are strong and are useful for making tools, buildings, bridges and other structures where strength is important. The most abundant metal on the earth is iron.The tallest free-standing structures in the world are made of metals, primarily the alloy steel. They include the Dubai skyscraper Burj Kalifa, the Tokyo television tower Skytree, and the Shanghai Tower skyscraper. Some of the examples of metals are copper, gold, iron, aluminium, etc.

Properties of metals

Physical properties

• State: Most of the metals are solid at ordinary temperature except mercury.
• Hardness: Most of the metals are generally hard in nature.
• Lustre: Metals possess metallic lustre when they are freshly cut.
• Density: Metals have relatively high densities except lithium, sodium and potassium.
• Malleability: Metals can be beaten into a thin plate, such property is called malleability.
• Ductility: The property of metal being made into wires is called ductility and the metal is called ductile.
• Conductivity: Metals are generally good conductors of heat and electricity.
• Melting and boiling point of metal: The melting and boiling point of metals are generally high due to their high density and hardness.
• Electric charge: Metals are electropositive elements which give cations when ionized. In aqueous solutions, metallic salts undergo ionization and produce metallic ions.

Chemical properties

• Reaction with oxygen: When metal is treated with oxygen on heating they react together to give basic oxides.
  4Na + O2→ 2Na2O
• Reaction with Hydrogen: Metals like sodium, potassium, and calcium burn in hydrogen and forms corresponding halides.
  2Na + H2→ 2NaH (sodium hydride)
  2K + H2→ 2KH (potassium hydride)
• Reaction with acids: Most of the reactive metals like sodium, potassium and calcium react with dilute acid to form salts and hydrogen gas.
  Zn + 2HCl→ ZnCl2 + H2

Non- Metals

Non- metals are the bad conductor of heat and electricity. They are found mostly in the gaseous form. Some of the examples of non- metals are elements like hydrogen, nitrogen, oxygen, phosphorous, chlorine etc. They are electronegative in nature. Non- metals are found in earth's crust and atmosphere. The human body also contains non- metals. The hardest and most precious non- metal is a diamond. Some of the properties of non- metals are given below,

Properties of Metals

Physical properties

• They are bad conductors of heat and electricity except graphite.
• They are non- malleable.
• They are non- ductile.
• They have low melting point and boiling point.
• They are found in all three state i.e.solid, liquid and gas.
• They are transparent and do not have metallic lusture except graphite and diamond.
• They are soft. (except diamond)
• Non- metals are not sonorous.

Chemical Properties

• Oxides of non- metals are either acidic or neutral in nature.
• They behave as oxidizing agents.
• They react with hydrogen to produce covalent compounds.
• They have a tendency to receive electrons.

Differences between metals and non-metals are given in a table below:

Properties	Metals	Non-metals
State	All, except mercury, metals are solid at ordinary temperature.	Non-metals are found in all three states at ordinary temperature.
Metallic lusture	They possess metallic luster when they are freshly cut. Except lithium.	Non-metals except Iodine and graphite, do not possess any metallic luster.
Hardness	They are generally hard because the molecules are closely packed in them.	They are generally soft in nature except diamond.
Breakability	They are hardly broken into pieces.	They can be easily broken.
Melting and boiling point	The melting and boiling points of metals are generally high.	They have usually low melting and boiling points.
Metallic clink	Metals, when struck with a hammer emit a peculiar sound called metallic clink.	They do not emit any metallic sound.
Malleability	They can be beaten into thin plate except antimony, arsenic, and bismuth. Such property is known as malleability.	They are non-malleable.
Ductility	Wire can be made from metals. Such property is known as ductility.	They are non-ductile.
Conductivity	They are generally good conductors of heat and electricity.	They are poor conductors of heat and electricity except graphite.
Specific gravity	They have high specific gravity except Li, Na, K, Ca etc.	They have low specific gravity except diamond.
Electrochemical behavior	They form cations or electropositive ions by the loss of electrons.	They form anions or electronegative ions by the gain of electrons.
Alloy formation	Metals have the dissolving power to the other metals to form a homogenous mixture.	They generally do not form alloys.
Reaction with oxygen	Metals forms basic oxides.	Non-metals form an acidic oxide.
Reaction with hydrogen	Metals rarely combines with hydrogen to form unstable hydrides.	Non-metals usually combine with hydrogen to give stable hydrides.
Reaction with acids	Most of the metals reacts with dilute acids to form salts and hydrogen.	Usually non-metals do not form salts.

Metalloids:

The elements that show the properties of both metals and non-metals are called metalloids. Examples of metalloids are arsenic, antimony and germanium.

Metalloids possess the following characteristics:

• They are a poor conductor of heat and electricity.
• They possess metallic luster.
• They form alloys.
• They are neither malleable nor ductile.

Alloys:

An alloy is defined as a homogeneous mixture of two or more metals and non-metals. For example, brass is an alloy of copper and zinc.

Alloys have the following properties:

• Generally alloys are harder than their components.
• They are good conductors of heat and electricity.
• They have low melting point.
• Alloys increase the strength of metals.
• They are malleable and ductile.